JP2814799B2 - Contact charging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact-type charging device in which a charging member is brought into contact with a member to be charged and a voltage is applied to the charging member to charge the member (including static elimination).

[0002]

2. Description of the Related Art For example, in an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, a process of charging a surface of an image carrier as a member to be charged such as an electrophotographic photosensitive member or an electrostatic recording dielectric is executed. Conventionally, a non-contact type corona discharge device has been used as a charging device. Although the corona discharge device has advantages such as good charging performance, it also has many problems such as requiring a high-voltage power supply and generation of corona discharge products such as ozone.

In recent years, a contact (direct) charging method in which a charging member such as a blade type or a roller type to which a voltage is applied is brought into contact with the surface of the member to be charged to a predetermined polarity and potential. The device has been used as a charging means instead of a corona discharge device. The contact-type charging device has the advantages that the pressure of the power supply can be reduced and the generation of corona discharge products such as ozone is extremely small.

As a specific example, FIG. 5 shows a schematic configuration of a charging device using a blade-shaped charging member (charging blade) (for example, JP-A-1-93760). Reference numeral 1 denotes a member to be charged, which is, for example, a rotating drum type photoconductor (hereinafter, referred to as a photoconductor drum) of an electrophotographic apparatus. This photosensitive drum 1
Is a predetermined peripheral speed (process speed) in the clockwise direction indicated by the arrow.
Is driven to rotate.

Reference numeral 10 denotes a charging blade as a charging member, which is formed on a blade-like (plate-like) elastic body (for example, rubber) having a medium resistance value as an electrode layer and a photosensitive drum contact surface at a tip end thereof. Made of the insulating coating layer 10a. The base side of the charging blade is fixedly held on a support 11, and the blade is directed to the surface of the photoreceptor drum 1 in the direction opposite to the rotating direction of the drum (counter direction) in this case, and the coating layer at the tip end is fixed to the blade. It is pressed against the surface of the photoreceptor drum due to elasticity.

By applying a voltage from the power supply 3 to the charging member 10, the surface of the rotating photosensitive drum 1 is charged by a contact method. An image forming process device such as an exposure unit, a development unit, and a transfer unit is arranged around or near the photosensitive drum 1 to constitute an electrophotographic apparatus, but these are not shown in the figure.

The voltage applied to the charging member 10 may be only a DC voltage, but charging can be performed uniformly by applying an oscillating voltage (a voltage whose voltage value changes periodically with time). 63-149668, etc.). For example, by applying an oscillating voltage obtained by superimposing a DC voltage Vdc on an AC voltage Vac having a peak-to-peak voltage that is twice or more the charging start voltage of the object to be charged when a DC voltage is applied, the charging of the object to be charged is evened out. Therefore, uniform charging can be performed. The waveform of the oscillating voltage is not limited to a sine wave, but may be a rectangular wave, a triangular wave, or a pulse wave. The AC voltage includes a rectangular wave voltage formed by periodically turning on and off a DC power supply. By applying only the AC voltage, the object to be charged is removed.

[0008]

When an oscillating voltage is applied, the effect of equalizing the charging of the member to be charged is as follows: the part of the separation (interval) between the member to be charged 1 and the charging member (electrode) 10 It has been confirmed that the greater the number, the greater the effect.

In the case of the charging blade 10 described above, the contact surface (contact surface) with the photosensitive drum 1 as a member to be charged, that is, the charged area is entirely an electrode layer, so that there is only one separation portion. The effect of leveling the charge cannot be sufficiently exerted, and poor charging is likely to occur.

[0010] Further, the charging member vibrates due to the AC component of the vibration voltage, and a vibration sound called "charge sound" is generated. In the case of the charging blade 10 described above, since the entire charging region N is an electrode layer, the area of the electrode in contact with the photosensitive drum is large. For this reason, there is a problem that the generated charging noise is very loud and gives a feeling of discomfort. The problem of generation of charging noise is the same even when the charging member is a roller type, a rod type, or the like.

An object of the present invention is to provide a contact-type charging device having stable and uniform charging characteristics.

Another object of the present invention is to provide a contact-type charging device in which charging noise during charging is quiet.

[0013]

SUMMARY OF THE INVENTION The present invention is a contact-type charging device having the following configuration.

(1) A charging member that contacts a member to be charged to charge the member, an electrode layer to which a voltage is applied, a coating material provided on a surface that contacts the member, and In a contact-type charging device having a charging member comprising, the total surface area of the electrode layer at the contact portion between the charging member and the member to be charged,
A contact-type charging device, wherein the contact area is smaller than a contact area between the charging member and the member to be charged.

(2) The electrode layer is composed of a plurality of electrodes, and has a pattern configuration in which an arbitrary point on the member to be charged crosses two or more electrodes when passing through the contact surface between the charging member and the member to be charged. The contact-type charging device according to (1), wherein

(3) The contact-type charging device according to (1) or (2), wherein the voltage applied to the electrode layer is an oscillating voltage.

(4) The contact-type charging device according to (3), wherein the oscillating voltage is a superimposed voltage of an AC voltage and a DC voltage.

(5) The object to be charged is a photosensitive member of the image forming apparatus.
Characterized by being a rotating image carrier such as a dielectric (1)
The contact-type charging device according to any one of (1) to (4).

(6) The charging member is fixed and supported substantially parallel to the tangential direction of the rotating direction of the charged body, so that the contact surface of the rotating surface of the charged body with the charged body is fixed and the charged member is fixed to the surface of the charged body. The member that is in contact and supports the electrode layer is SR
The contact-type charging device according to any one of (1) to (5), which is an elastic body having a hardness defined by IS 0101 of 5 to 75 °.

[0020]

[Action] The total surface area of the electrode layer within the contact area of the contact portion between the charging member and the member to be charged is made smaller than the area of the contact portion between the charging member and the member to be charged. Where L (mm) is the width of the electrode layer in the rotating direction of the charged body, the width of the electrode layer of the electrode layer (the width of the charged layer in the rotating direction) is L (mm)> electrode line width (mm) ≧ L × (1 / 50) (mm), the total area of the surface of the electrode layer in the charging region is reduced, and the generated charging noise can be reduced.

If the electrode line width is larger than L (mm), the charging noise is undesirably increased. L × (1/50) (m
If the thickness is smaller than m), a large load is applied to the electrode layer when a voltage is applied to the electrode layer, and the durability is deteriorated.

[0022] As described above, it has been confirmed that, as described above, the effect of the charging property of the charging member increases as the distance between the electrodes increases, and that when a voltage is applied to the electrode, the periphery of the electrode becomes the distance.

Therefore, the electrode layer is composed of a plurality of electrodes,
When any point on the charged object passes through the contact portion between the charged member and the charged object, the pattern configuration is such that it crosses two or more electrodes. Is obtained.

[0024] The charging member has a uniform coating material on the contact surface with the member to be charged, and has a coating layer covering the outside of the electrode layer, and the electrode layer faces the member to be charged via the coating layer. Thus, wear and damage due to mutual direct contact between the electrode layer and the member to be charged can be prevented, and the coating layer has a resistance value of 1 × 10 ^{5 to} 5 × 10 ⁸ Ω.
When a low withstand voltage defect portion such as a pinhole or a damaged portion exists on the surface of the member to be charged, it is possible to prevent the occurrence of charging failure due to the phenomenon of concentrated leakage of charging current from the electrode layer to the defect portion.

[0025] The charging member is fixed and supported substantially in parallel with the tangential direction of the rotation direction of the charged body, and the contact surface of the rotating surface of the charged body with the charged body is fixed to be brought into contact with the charged body surface, so that the charged area is formed. It can be easily kept wide, and therefore stable charging characteristics can be maintained. Further, it is not necessary to increase the contact accuracy for keeping the charged area uniform.

[0026] The elastic body serving as the electrode layer support member of the charging member has an effect of uniformly contacting the electrode layer with the member to be charged due to its elasticity, or a function of uniformly contacting the electrode layer via the coating layer. It acts to reduce the charging noise by absorbing the vibration of the charging member due to the applied vibration voltage.

The reason for setting the hardness of the elastic body to 5 to 75 ° in terms of the hardness of SRIS 0101 is a characteristic necessary for uniformly contacting the electrode layer with the member to be charged. It is not preferable because "set" occurs in the elastic body. On the other hand, if the hardness is 75 ° or more, it becomes impossible to follow minute irregularities of the member to be charged at the contact portion between the member to be charged and the member to be charged.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram of a contact type charging device according to the present invention.

Reference numeral 1 denotes, for example, a photosensitive drum as a member to be charged. Reference numeral 5 denotes a charging member, which is a laminate of an elastic layer 5c as an electrode layer support, an electrode layer 5b, and a coating layer 5a in this order. The coating layer 5a side is the contact surface side with respect to the photosensitive drum 1.

The charging member is substantially parallel to the tangential direction of the rotation direction of the photosensitive drum 1 and the elastic layer 5
The c side is fixed and supported, and the contact surface of the photosensitive drum rotating surface with the drum is fixed, and the drum surface is brought into pressure contact with the drum surface by the elastic characteristics of the elastic layer 5c. L indicates a contact portion between the charging member 5 and the photosensitive drum 1, a width of the contact portion, or a charged portion.

A voltage is applied to the electrode layer 5b from the power supply 3, and a bias is applied to the photoconductor via the coating layer 5a to charge the photoconductor.

(1) Elastic layer 5c For example, natural rubber, isoprene rubber, butadiene rubber,
1.2-polybutadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, butyl rubber, ethylene-propylene rubber, chlorosulfonated polyethylene rubber, acrylic rubber, epichlorohydrin rubber, polysulfide rubber, silicon rubber, fluorine rubber, urethane rubber, etc. Can be used.

As described in the above-mentioned section of the operation, the hardness used in SRIS 0101 is 5 ° to 75 °. Further, since the elastic layer 5c supports the electrode layer 5b, it is preferably flame-retardant.

(2) Electrode Layer 5b The electrode layer 5b is preferably made of a nonmetallic material having flexibility at room temperature, from the viewpoint of the stability of the contact state in the charged portion L. For example, a material having a resistance value of 1 × 10 ³ Ω or less by adding a conductive pigment to an organic substance is preferable. The measurement of the resistance value in the present invention was performed according to JIS K-6911.

Examples of the organic substance include resins such as polyamide, polyimide, polyurethane, polyvinyl alcohol, silicon, and polyester. And the same kind of resin as the coating layer 5a is preferable from the adhesiveness with the coating layer 5a mentioned later.

Examples of the conductive pigment include carbon black, carbon graphite, zinc oxide, titanium oxide, metal particles and the like.

The reason why the conductive pigment is dispersed in these organic materials as the electrode layer 5b is to prevent the elastic deformation of the elastic layer 5c from being hindered. It is not possible to follow minute irregularities, and it is easy for poor charging to occur. If the contact pressure is increased to improve this, the rotational torque of the photosensitive drum increases, which is not preferable.

Further, as described in the section of the operation, the total surface area of the electrode layer 5b within the contact area of the contact portion L between the charging member 5 and the photosensitive drum 1 is made smaller than the area of the contact portion L. Thereby, the charging noise is reduced.

As described in the section of the operation, the electrode layer 5b is composed of a plurality of electrodes, and any point on the photosensitive drum 1 passes through the contact portion L between the charging member 5 and the photosensitive drum 1. In this case, the uniform chargeability is improved by forming a pattern configuration having a relationship across two or more electrodes.

FIG. 2 shows a specific example of such an electrode pattern.
As shown in FIG. Reference numeral 51 denotes a plurality of individual electrode wires. 5
"d" indicates a power supply terminal common to the electrode lines 51, and a voltage is applied to this terminal.

(3) Coating Layer 5a As the coating layer material, a material having flexibility, lubricity and the like at room temperature due to the stability of the contact state in the charged portion L and the wear of the photoreceptor is preferably used.

For example, polyamide, polyimide, polyurethane, polyvinyl alcohol, Teflon, silicon, polyester and the like can be mentioned.

In order to adjust the resistance value, a conductive pigment may be appropriately added. Examples of the conductive pigment include carbon black, zinc oxide, titanium oxide, and metal particles.

The resistance value of the coating layer 5a in the present invention is in the range of 1 × 10 ^{5 to} 5 × 10 ⁸ Ω. As shown in FIG. 4, the electrode layer 5b is grounded,
A probe 6 of φ1 to which a DC voltage (250 V) is applied is pressed on “a” to measure the resistance. 7, a DC power supply; and 8, an ammeter. That is, since the resistance of the electrode layer 5b is sufficiently lower than the resistance of the coating layer 5c, the resistance value by the measuring method as shown in FIG. 4 is determined by the coating layer 5a.

When the resistance value of the coating layer 5a is 1 × 10 ⁵ Ω or less, if the photoconductor 1 is damaged, a withstand voltage cannot be obtained, which is not preferable. On the other hand, when the resistance is 5 × 10 ⁸ Ω or more, a current does not flow and charging failure occurs, which is not preferable.

The thickness of the coating layer 5a is 5 to 5
When the thickness is 5 μm or less, when a defect occurs on the photosensitive member, the applied bias is applied to the coating layer 5.
Undesirably, dielectric breakdown occurs due to concentration at a.
On the other hand, when the thickness is 500 μm or more, the elastic deformation of the elastic layer 5c is inhibited, which is not preferable.

(4) Manufacturing Method of Charging Member 5 As a manufacturing method of the charging member 5, for example, the electrode layer 5b is formed on the elastic layer 5c by coating and printing, and the coating layer 5a is coated and printed thereon. It can be manufactured by forming by such as.

In order to form a layered structure, a method of curing a material applied or printed on the elastic layer 5c, a thin film of each layer 5c, 5b, 5a is prepared in advance,
There is a method of sequentially bonding and laminating them.

When the layers 5c, 5b and 5a are bonded, the resistance of the adhesive used between the electrode layer 5b and the coating layer 5a is measured as the resistance of the coating layer 5a.
It is necessary that the resistance value is equal to that of the electrode layer 5b. In this case, if the adhesive layer is present on the entire surface of the contact portion L, there is no point in forming the pattern on the electrode layer 5b. Therefore, the adhesive layer is formed according to the electrode pattern 51 or the coating layer 5a is formed. It is necessary to make it according to the electrode pattern 51.

As another forming method, for example, there is a method of forming a thin film of the coating layer 5a, forming the electrode layer 5b thereon, and bonding the electrode layer 5b to the elastic layer 5c. In this case, the adhesive layer is not involved in the resistance,
It is not necessary to define both the resistance value and the application area.

(5) Effective test The following a) to g) types of charging members A to G according to the present invention were prepared, and each of them was charged by the primary charging means of the photosensitive drum of the process cartridge of the copying machine FC-2 manufactured by Canon Inc. As a member, it was installed in the same manner as in FIG. 1 and used in an actual machine. The following 1) charging performance test and 2) charging noise test were performed.
Table 1 summarizes the results.

The charging member was arranged with its contact portion adjusted such that the contact surface with the photosensitive drum, that is, the charging area width L was 5 mm or more. A DC voltage of 70 is applied to the electrode layer of the charging member.
The charging performance and charging sound were evaluated by applying a bias of 0 V, an AC voltage of 2400 V, and a frequency of 350 Hz.

As a comparative example, the following charging member H was prepared, and the same test was conducted. The results are shown in Table 1.

A) Charging member A SRIS 0101 Foamed urethane having a hardness of 20 ° is used as the elastic layer 5c, and an electrode material which is a conductive paint by adding conductive graphite to a two-component curable urethane resin is used.
The electrode layer 5 is formed on the surface of the elastic layer 5c by screen printing.
Print-formed as b. The electrode layer 5b after printing is 80 ° C.
Heat crosslinking treatment was performed for 30 minutes.

At this time, the printing pattern of the electrode layer 5b is composed of a plurality of parallel electrode lines 51 having an electrode line width of 1 mm and an inter-line distance of 1 mm, as shown in FIG. The pattern was perpendicular to the direction.

The elastic layer 5c is cut out in a size of 250 mm in length in parallel with the electrode layer pattern and 12 mm in size perpendicular to the electrode layer pattern by a punching die, and a power supply terminal 5d is attached to the longitudinal end using an electrode material. .

As a coating material, a two-component curable urethane (100
Parts by weight), a 30 μm coating layer 5a is formed on the electrode layer 5b by a silk printing method using a paint whose resistance is adjusted by adding conductive titanium oxide (180 parts by weight).
Crosslink by heating at 0 ° C. for 30 minutes.

B) Charging member B In the charging member A, the printing pattern of the electrode layer 5b is changed to the electrode line width 0.5 mm and the line interval 0.5 mm, and the other charging members are the same as the charging member A.

C) Charging member C In the charging member A, the printing pattern of the electrode layer 5b is changed to an electrode line width of 0.5 mm and a line spacing of 1 mm, and the other charging members are the same as the charging member A.

D) Charging member D In the charging member A, the printing pattern of the electrode layer 5b is changed to the electrode line width of 0.5 mm and the line interval of 1.5 mm.

E) Charging member E In the charging member A, the printing pattern of the electrode layer 5b is changed to an electrode line width of 0.3 mm and a line interval of 0.5 mm.

F) Charging member F In the charging member A, the printing pattern of the electrode layer 5b is changed to 0.3 mm in electrode line width and 1 mm between lines, and the other charging members are the same as the charging member A.

G) Charging member G In the charging member A, the printing pattern of the electrode layer 5b is changed to 0.3 mm in electrode line width and 1.5 mm between lines, and the other charging members are the same as the charging member A.

H) Charging member H (Comparative example) The printing pattern of the electrode layer 5b was such that the electrode line width was larger than the width of the charged area in the rotation direction of the photosensitive drum. Other configurations are the same as those of the charging member A.

1) Charging Performance The charging performance was evaluated based on the convergence of potential. After the photosensitive drum is neutralized, the above-described bias is applied to the electrode layer 5b of the charging member to continuously charge the photosensitive member, and the surface potential of the photosensitive member is measured by a surface voltmeter. The evaluation was made based on the difference between the potentials of the photoreceptor in the fifth and first rounds.

Evaluation ◎: Absolute value of difference is within 5 V Evaluation ：: Absolute value of difference is within 5 to 10 V Evaluation △: Absolute value of difference is within 10 to 20 V Evaluation X: Absolute value of difference is 20 V or more 2) Charge Sound The copier equipped with the charging member was set in an anechoic room, and the noise during charging was measured. The measurement was made according to ISO 77
The procedure was performed in accordance with paragraph 6 of 79.

[0067]

[Table 1] From the test results of the charging member A and the charging member H of the comparative example,
When the area of the charged region is the same, it can be seen that if the number of the electrodes 51 existing in the charged region increases, the portion of the separated portion increases and the chargeability improves, and if the total surface area of the electrode decreases, the charging noise decreases. .

According to the test results of the charging members B, C, and D, when the charging area is the same and the electrode line width is constant and the pitch between the lines is changed, the charging property is narrow, that is, the charging area is small. It is preferable that the charging member B has a large number of separated portions, and that the charging noise is low when the pitch width is wide because the surface layer area of the electrode is small. I understand.

From the test results of the charging members B and E, the charging members C and F, and the charging members D and G, the electrode line width was reduced while the charging area was the same and the pitch between the lines was constant. In this case, it can be seen that the chargeability is improved because the portion of the separation portion existing in the charged area is increased, and the charging sound is quiet because the total surface area of the electrode is reduced.

[0070]

As described above, according to the present invention, the contact-type charging device has a stable and uniform charging characteristic, and the generated charging sound is quiet even when charging is performed by applying an oscillating voltage to the charging member. You can get something.

[Brief description of the drawings]

FIG. 1 is a schematic structural view of a contact-type charging device according to the present invention.

FIG. 2 shows an example of an electrode layer pattern (part 1).

FIG. 3 is a pattern example of an electrode layer (part 2).

Fig. 4 Measurement procedure of resistance value of coating layer

FIG. 5 is a schematic view of a blade type device as a conventional example of a contact type charging device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum as charged object 3 bias application power supply 5 charging member 5c elastic layer (electrode layer support member) 5b electrode layer 5a coating layer 6 probe 7 DC power supply 8 ammeter 10 charging blade 11 blade support member

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Goto 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Tatsuichi Tsukita 3-30-2 Shimomaruko, Ota-ku, Tokyo (56) References JP-A-57-67951 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/02 101

Claims (6)

(57) [Claims] 1. A method for charging an object to be charged, comprising the steps of:
A charging member that touches, an electrode layer to which a voltage is applied,
A coating material provided on a surface in contact with the member to be charged;
In the contact type charging device having that charging member, contact the total surface area of the electrode layer at the contact portion between the belt conductive member and the member to be charged, characterized in that narrower than the contact area between the charging member and the charged member Type charging device. 2. An electrode layer comprising a plurality of electrodes, having a pattern configuration in which an arbitrary point on a member to be charged crosses two or more electrodes when passing through a contact surface between the charging member and the member to be charged. 2. The contact-type charging device according to claim 1, wherein: 3. The contact-type charging device according to claim 1, wherein the voltage applied to the electrode layer is an oscillating voltage. 4. The contact-type charging device according to claim 3, wherein the oscillating voltage is a superimposed voltage of an AC voltage and a DC voltage. 5. The contact-type charging device according to claim 1, wherein the member to be charged is a rotating image carrier such as a photoreceptor or a dielectric of an image forming apparatus. 6. The strip conductive member is to be charged member surface contact face is fixed to the member to be charged in the charge-receiving member rotating surface by tangential direction substantially be parallel to fixed support in the rotational direction of the member to be charged The member that is in contact and supports the electrode layer is SRIS
Claims 1 to same, characterized in that at hardness defined by 0101 is an elastic body having a 5-75 ° hardness
5. The contact-type charging device according to any one of 5 .